It is well established that certain pulmonary toxins and carcinogens act on specific cell types of the rodent lungs. Metabolism studies in vivo, or experiments using whole organ homogenates and fractions, may therefore not be suited to detect metabolic pathways operative in such specific cell types. It is the objective of this project to isolate and selectively grow the major epithelial cell types of the rat and hamster lung for comparative studies on their biology and response to toxins, carcinogens and anticancer drugs. These defined cell populations will be used for comparative studies on the effects of various pulmonry agents on human lung cancer cells lines. Immunoperoxidase staining of isolated rat lung epithelial cells with an antibody preparation specific for rat surfactant apoproteins has revealed that rat alveolar type II cells can be purified to 95% by selective plating and proliferation. These cells which proliferated in vitro were shown to retain their epithelial morphology and contained osmiophilic bodies for 5 days in culture. This specific antisera preparation revealed that the isolated type II cells retained the capability to produce surfactant-like material. Using immunoperoxidase method, two patterns of staining were observed, one being a diffuse cytoplasmic stain and the other consisting of intensely stained cytoplasmic structures. These different patterns may reflect different stages of maturation of lamellar structures during the production and secretion of lung surfactant apoprotein. Analysis of phospholipid biosynthesis revealed that the isolated alveolar type II cells actively converted choline into phosphatidylcholine and that the prosynthetic activity increased wth time in culture. The morphology of the isolated type II cells as well as other isolated cell types was characterized by a newly established technique which allows for correlative morphological characterization by light and electron microscopy.